The team also grew batches of MRSA with and without sugar syrup, to check whether the honey's high sugar content was solely responsible for fighting the bacteria.

In general, many bacteria can't grow in high-sugar environments, since the sugars tie up water that the bacteria need to survive. (Get more germ-filled facts with our infectious diseases quiz.)

Jenkins and colleagues found that the MRSA bacteria treated with manuka honey more often lacked a particular protein necessary for synthesizing fatty acids, which are required for building cell walls and internal structures.

The crippled bacteria "don't have the necessary proteins to complete their life cycles," Jenkins said, so they are unable to reproduce and eventually die.

Since the sugar syrup didn't have the same results, the researchers think some other, unidentified component must be disabling the bacteria.

Not Exactly on Store Shelves

Finding out more about manuka's mystery ingredient could lead to new treatments for drug-resistant bacteria strains, the study authors say.

Still, the researchers caution against treating wounds with commercially sold manuka honey.

Unlike medical-grade honey, store-bought honey is not sterilized and could contain microbes and spores that might make an infection worse, Jenkins said.

Findings presented September 7 at the annual meeting of the Society for General Microbiology in Edinburgh, Scotland.